At first glance, gamba grass appears to fit right into Australia’s natural landscape, but the tall green tussocks are an insidious threat to native animals, homes and lives.
- Gamba grass competes with native plants and can increase fire fuel loads by eight times
- The weed is widespread through the Northern Territory and Queensland
- WA is the only state to come close to the eradication of gamba grass
Native to Africa’s savannas and growing to four meters, gamba grass was introduced to the Northern Territory in 1931 for testing as cattle feed.
It was brought to Queensland in 1942, and large-scale planting took place in the 80s as it took hold in Western Australia’s east Kimberley region.
It wasn’t until 2012 that it was recognized as a weed of national significance, competing with native plants and acting as a dangerous accelerant during Australia’s increasingly ferocious bushfires.
Department of Biodiversity, Conservation and Attractions (DBCA) conservation coordinator David Chemello said while the native Australian species had adapted to fire, they stood no chance against a gamba grass fire which could increase fire fuel loads by eight times.
As the NT and Queensland continue an uphill battle against the invasive pest, WA is close to eradicating it.
Plant numbers decline
Mr Chemello said DBCA started a control program in 2011 and by 2018 were able to count just 3,000 plants.
“By the next year it was down to 300, by 2020 it was down to 23 individual plants and last wet season it was eight plants that were found and controlled,” Mr Chemello said.
“This is textbook eradication and as close to being finished as we could possibly hope for so it’s pretty exciting stuff.”
But he warned the battle was not over yet with success stories being “very far and few between”.
The DBCA team still has years of work ahead of it.
“We still need to go out for probably another five years in the monitoring phase of the program and that’s just to ensure that any seed that is left in the soil has been exhausted,” he said.
Mr Chemello said DBCA had many programs running to reduce or eradicate invasive plants, including a rubber vine program which was on track but still had about a decade before completion.
Like gamba grass, rubber vine was out of control in Queensland and Mr Chemello attributed WA’s success to early intervention.
“We got onto these weeds when we still had a chance, if there was 10 million hectares in WA, eradication wouldn’t even come into the picture but the area was quite small,” he said.
“Even though it is a small area it involves a lot of dedication to these projects year after year.
A different situation across the border
While DBCA is close to entering the monitoring phase, across the border in the Northern Territory conservationists continue their battle to contain gamba grass.
Pew Charitable Trusts’s Mitch Hart said the global not-for-profit championed conservation efforts in Australia, including a partnership with the Gamba Grass Roots Alliance.
“We focus on Australia’s outback because it’s globally significant. It’s still overall in pretty good nick, but it needs active management,” Mr Hart said.
“That’s why we work on the gamba issue, because we see it as a risk to some of Australia’s most intact tropical savanna.”
Mr Hart said gamba grass was a “triple threat” with large infestations from Darwin to Katherine.
“It’s a threat to people’s lives, it’s a threat to the economy of the Northern Territory, and then it has the environmental impacts of reducing and totally destroying Australia’s northern savanna,” he said.
Gamba grass was the only weed listed as a priority threat in the federal government’s Threatened Species Action Plan 2021-2026.
“That’s a real recognition of just how bad gamba can be and the threat it poses to native wildlife,” Mr Hart said.
No guarantees with funding
Mr Hart said while the NT government had committed $500,000 to the Gamba Army to fight the prolific weed, the federal government needed to commit funding if there was any chance of reduction, not just containment.
“The good news is that there’s programs that are up and running that are popular, such as the Gamba Army and a new 10-year plan,” he said.
“But what we know is it needs more effort [and] more support if we’re actually going to do the job of reducing gamba in that area.”
Mr Chemello said funding hung in the balance every year for weed eradication programs.
Despite being the least impacted, WA was the only state mentioned in the federal government’s action plan as a priority target to eradicate gamba grass.
But the DBCA’s gamba grass program had no federal funding and was made up of contributions from the State Natural Resource Management Program, Parks and Wildlife, Department of Primary Industry and Regional Development and the Kimberley Rangelands Biosecurity Association.